The diagnosis and treatment of patients with cancerous tumors, pre-malignant conditions, and other disorders has long been an area of intense investigation. Non-invasive methods for examining tissue include palpation, X-ray, magnetic resonance imaging (MRI), computed tomography (CT), and ultrasound imaging. When a physician suspects that tissue may contain cancerous cells, a biopsy may be done using either an open procedure or a percutaneous procedure. For an open procedure, a scalpel is used to create a large incision in the tissue to provide direct viewing and access to the tissue mass of interest. The entire mass (excisional biopsy) or a part of the mass (incisional biopsy) may then be removed. In most percutaneous biopsy procedures, a needle-like instrument is inserted through a very small incision to access the tissue mass of interest and obtain a tissue sample for later examination and analysis.
Aspiration and core sampling are two percutaneous methods for obtaining a portion of tissue from within the body. In an aspiration procedure, tissue is fragmented into pieces and drawn through a fine needle in a fluid medium. The method is less intrusive than most other sampling techniques, however, it has limited application since the structure of tissue excised by aspiration is destroyed leaving only individual cells for analysis (cytology) and not the tissue structure for analysis (pathology). In core biopsy, a core or fragment of tissue is obtained in a manner, which preserves both the cells and the structure for histological examination. The type of biopsy used depends mainly on various factors, and no single procedure is ideal for all cases. Core biopsy, however, is very useful in a number of conditions and is widely used by physicians.
Examples of core sampling biopsy instruments are described in U.S. Pat. Nos. 5,562,822 and 5,769,086 (both issued to Ritchart, et al), and in U.S. Pat. No. 6,007,497 (issued to Huitema). Another example of a core sampling biopsy instrument is the biopsy instrument now marketed by Ethicon Endo-Surgery, Inc., Cincinnati, Ohio, under the trade name MAMMOTOME. Each of these instruments is a type of image-guided, percutaneous, coring, breast biopsy instrument, which uses a vacuum for retrieving tissue samples. A physician uses these instruments to capture “actively” (using the vacuum) tissue prior to severing it from the body. In particular, in these biopsy instruments, tissue is drawn into a port at the distal end of a piercing element, hereinafter referred to as a piercer. A cutting element, hereinafter referred to as a cutter, is rotated and advanced through a lumen of the piercer past the port. As the cutter advances through the port, it severs the tissue drawn into the port from the surrounding tissue. While the cutter is generally rotated using some type of motor, it may be advanced either manually or automatically. In the MAMMOTOME instrument, a disposable probe unit containing a piercer and cutter is first operationally connected to a reusable drive unit. The surgeon can then manually move the cutter back and forth by lateral movement of a knob mounted on the outside of the drive unit. Once the cutter is in place, proximal to the tissue port, further lateral movement of the knob is prevented and the cutter is advanced through the tissue port to sever tissue by twisting the knob. This arrangement is advantageous because the surgeon is able, through tactile and/or audible feedback, to determine whether the cutter is effectively cutting tissue or if there is a problem, such as binding, stalling, or an obstruction. The surgeon may then adjust the speed at which he moves the cutter through the tissue, stop the cutter or back the cutter away from the tissue. Since the surgeon can feel, through tactile feedback, at what point the cutter encounters an obstruction such as when it has reached its limits of linear travel, he will anticipate these obstructions and can readily control and stop the cutter at its most distal and proximal positions. Anticipating these obstructions and slowing or stopping the cutter translation just as the obstruction is reached thus avoids undo erratic movement of the instrument. Manual control of the cutter translation by the surgeon therefore allows the surgeon full control of the rate and distance of linear travel. Also, since each new disposable probe unit assembled to the reusable drive unit may vary in length slightly due to manufacturing tolerances, manual control by the surgeon allows for compensation for these size variations.
U.S. Pat. Nos. 5,562,822 and 5,769,086 describe automation of the translation of the cutter in a biopsy device to facilitate the procedure. However, if the procedure is automated as described in those references, the surgeon loses the benefit of the tactile feedback, which results when the cutter is advanced and retracted manually. It would therefore become necessary to require the cutter controlling means to know the precise condition, location, and travel distance of the cutter to ensure smooth and reliable operation of the biopsy system. In an automated biopsy system there may therefore be a need for the surgeon to follow a procedure to calibrate the cutter/probe unit prior to starting the surgical biopsy to ensure smooth and reliable operation. Such a calibration procedure would also be beneficial in confirming that the surgeon has selected the correctly sized biopsy probe for the software installed in the controlling means.
U.S. Pat. No. 6,086,544 (issued to Hibner, et al) describes a control apparatus for a surgical biopsy device. The biopsy device has a probe unit containing a rotatable, translatable cutter. The drive unit contains a cutter linear drive screw and cutter rotational drive screw. A control apparatus, containing drive motors, is connected to the drive unit through rotatable, flexible drive cables. A computing device is used to coordinate control of the rotation and linear translation of the cutter. This is accomplished by using optical sensors capable of providing very precise rotational position feedback information on the cutter linear drive screw and cutter rotational drive screw. Information supplied by these optical sensors to the computing device allows the computing device to control individual motors operating the drive cables connected to the cutter linear drive screw and cutter rotational drive screw. The computing device can therefore compare the actual performance of the biopsy device during the biopsy procedure to pre-established performance parameters and modify motor speeds to maintain system performance within pre-established parameters.
This system as disclosed however does not compensate for the aforementioned problem of the surgeon's lack of tactile feedback and control as the cutter reaches its limits of distal and proximal travel. This system reacts to the fact that the cutter's linear travel has reached its limit after the cutter has encountered a physical obstruction. Unfortunately the reaction time for the cable rotational sensors to detect the obstruction, send a message to the control apparatus, and the control apparatus terminate power to the cable drive motors may be too long to prevent the flexible, rotatable drive cables from twisting or “winding” do to the cutter's sudden and unexpected stop. If the user is not grasping the biopsy device tightly there is the risk the biopsy probe could inadvertently move and cause discomfort to the patent.
Another shortfall of this control system relates to its inability to compensate for different probe unit/drive unit combinations. Slight variations in cutter length, cutter position, or probe length occur due to manufacturing assembly procedures and tolerances. The manufacturer must accept certain manufacturing variations in order to make the device safe, functional, and affordable. Therefore, as a new probe unit is operationally connected to the reusable drive unit at the start of each biopsy procedure, the cutter linear travel distance and distal and proximal stopping points will be different from the preceding probe unit/drive unit combination. The probe manufacturer may also intentionally manufacture different “gauge” probes to different length specifications. The optical sensors could then be used to determine if the correctly sized probe is installed to match the software installed in the drive unit. Differently sized or “gauge” probes may therefore be manufactured to different length specifications so that, upon initial start-up, the clinician will be warned when an improper probe is installed for the software residing in the control unit.
Cutter rotational speed will also vary from one probe unit/drive unit combination to another due to manufacturing tolerances. It would, therefore, be advantageous to utilize the same optical sensors and computing device to establish the relative linear position and travel range of the cutter at initial start-up. They may also be used to establish whether or not excessive resistance is present within the cutter/probe unit that would cause the biopsy device to perform outside of the pre-established performance parameters, even before the biopsy device is put into actual clinical use.
What is therefore needed is a method in an automated core sampling biopsy device for determining the cutter's most distal and proximal linear travel position and providing feedback to the cutter control means for the purpose of establishing whether or not the cutter linear displacement is within a predetermined range before an actual biopsy procedure is performed. What is further needed is a method in an automated core sampling biopsy device for determining the rotational speed of the cutter and providing feedback to the cutter control means for the purpose of establishing whether or not the cutter rotational speed is within a predetermined range prior to a biopsy procedure.